feat: add link restore

README.md

@@ -116,10 +116,16 @@ dangling symlink instead of the contents, while the host resolves it as before.
 
 ```bash
 ahab link add .env secrets/         # move out, leave symlinks behind
+ahab link restore .env              # move it back into the repository
+ahab link restore --all             # everything this repo has in the store
 ahab link check                     # what a sandbox can still read
 ahab link check --porcelain         # `<code> <path>`, for scripts
 ```
 
+`restore` is the inverse of `add`: the file moves out of the store and back to
+where it was, and the store keeps nothing. A second checkout linking the same
+path is left with a dangling symlink, since there is only ever one stored copy.
+
 The store lives under
 `${XDG_DATA_HOME:-$HOME/.local/share}/ahab/<host>/<owner>/<repo>/`, derived
 from the git `origin` remote.